Venturi arrangement



1968 L. T. KAYSER VENTURI ARRANGEMENT Filed May 7, 1965 INVENTORZQ7'JLZr ATTORNEY FIG. 4

United States Patent ABSTRACT OF THE DISCLOSURE A venturi arrangementfor control of fluid passing therethrough substantially independent ofpressure variations downstream of the venturi arrangement in which fluidfed in axial direction of the venturi is deflected at the end of theinlet in direction substantially normal to the axis and passed through aradially outwardly extending annular gap which has a length and width sothat its peripheral cross section gradually increases in radiallyoutward direction to a cross section several times larger than itssmallest cross section so that the fluid cavitating and partlyevaporating in the region of the smallest cross section of the gap willrecondense in the latter to produce thereby a constant fluid flowthrough the venturi arrangement independent of pressure variationsdownstream of the gap.

In the field of control and measurement of fluid flow, as well as in thefield of hydraulic control arrangements, control means are necessary inwhich the amount of fluid flow passing through the control means iscompletely or at least nearly independent from the fluid pressuredownstream of the control means. Throttle valves, regulating pumps andcomplicated regulating arrangements have been used for this purpose,however, the above stated requirements have only to a limited degreebeen satisfied with such arrangements.

Lately, cavitating venturi tubes, comprising a convergent tube portionand a coaxial divergent tube portion joined to the smallest crosssection of the convergent tube portion and diverging at a very smallacute angle, have been used for controlling the flow of liquidssubstantially independent of the pressure downstream of the controlarrangement.

In such known venturi tubes the velocity of the flow of the liquidtherethrough increases until the static pressure of the liquid is equalto the vapor pressure of the liquid, whereby the liquid starts tocavitate with the result to limit the amount of liquid flowing throughthe venturi tube to a maximum value. The amount of flow of liquidthrough the venturi tube becomes independent from the pressuredownstream of the venturi tube due to this hydrodynamic effect.

To change the amount of fluid flow per time unit passing through such anaxial venturi tube it is necessary to change the smallest cross sectionof the passage, which may for instance be accomplished by a conicallytapering axial movable control mandrel coaxially arranged with theventuri tube and movable in axial direction into and out of the smallestcross section of the tube. The practical construction of sucharrangement is, however, rather difficult, especially in venturi tubesof small dirnensions in which the central mandrel has to be exactly Iguided which due to the necessarily close tolerances will result in anexpensive construction. Furthermore, it is practically impossible toproduce with such a construction a change of the throughput of liquidwhich is in linear relationship to the axial movement of the mandrel. Inaddition, the relationship of upstream fluid pressure to the "icemaximum allowable downstream fluid pressure will in such a venturi tubenot be constant over the whole control range, but this relationship willdepend to a great degree on the smallest cross section which is open atany time. Furthermore, the necessary sealing of the movable mandrelcomplicates such a construction and creates also undesired maintenanceproblems.

It is an object of the present invention to overcome these diflicultiesand disadvantages of known control means of the aforementioned kind,especially of venturi tubes with axial in and out flow.

It is an additional object of the present invention to provide a venturiarrangement operating according to the principle of a cavitating venturitube, which is usable as a regulating valve and which is simple inconstruction so it can be manufactured at very reasonable cost and willstand up trouble free under extended use.

It is an additional object of the present invention to provide a venturiarrangement of the aforementioned kind in which all sealing problems areeliminated.

With these objects in view, the venturi arrangement of the presentinvention basically comprises housing means having an axial inletpassage means for feeding a fluid, for instance liquid under pressureinto the housing means, and wall means defining an annular gap extendingin radia1 outward direction from the inlet passage means. Deflectormeans are also provided which extend substantially normal to the axis ofthe inlet passage means and which are arranged opposite and spaced fromthe inner end thereof for deflecting the axial stream of fluid passingthrough the inlet passage means in radial outward direction and the wallmeans defining the annular gap extend from the space between the innerend of the inlet passage means and the deflector means in radial outwarddirection to guide the fluid in a sheet-like annular stream in radialoutward direction. The adiabatic evaporation taking place in thesmallest cross section of the annular gap will produce such an increaseof the specific volume of the fluid passing therethrough that the amountof fluid passing per time unit through the arrangement will besubstantially constant and substantially independent from the fluidpressure downstream of the arrangement while the downstream fluidpressure is less than the inlet fluid pressure. Thereby it is importantthe the cross section of the annular gap downstream of the smallestcross section thereof increases gradually so that the condensation ofthe mixture of saturated vapor passing therethrough can take placeduring a sufliciently long time and in a stable manner. The logitudinalcross section of the annular gap has therefore to be formed accordinglyin such a manner that the peripheral flow cross section of the annulargap increases gradually in radial outward direction to a cross sectionwhich is several times larger than the smallest peripheral crosssection.

The deflector means may comprise a flexible membrane forming part of thewall means defining the aforementioned annular gap, which membrane is atits outer perighery fixed t0 the housing means. Such an arrangementincludes further means engaging substantially central portion of themembrane at the surface thereof facing away from the inner end of theinlet passage means for moving the central portion of the membranetoward or away from the inner end of the inlet passage means to changethereby the axial thickness of the annular gap. The deflector means mayalso be constituted by an axially movable piston arranged opposite theinner end of the inlet passage means and having preferably a convexlycurved surface facing the inner end of the inlet passage means.

The arrangement may also comprise spring means having a characteristicchanging according to a linear or square function and acting on acentral portion of the membrane or on the piston in a direction oppositeto the force imparted thereto by the pressure of the fluid passing intothe housing through the inlet passage means and impinging on themembrane or the piston. The arrangement may also include fluid passagemeans communicating with the inlet passage means and guiding fluid withsubstantially the same pressure as will reside in the inlet passagemeans to the surface of a central portion of the membrane or to themovable piston which faces away from the inner end of the inlet passagemeans so that the same pressure will act on opposite sides of themembrane or the piston, whereby the arrangement will become independentfrom fluid pressure variations upstream of the venturi arrangement.

The axial adjustment of the central portion of the membrane or of thepiston, necessary for the control of the amount of fluid flowing throughthe arrangement, can also be produced by screw means acting on the rearface of the membrane or the piston. The pitch of the screw thread of thescrew means is preferably chosen in such a manner that the total desiredadjustment of the axial thickness of the annular gap can be producedwith a single revolution of the screw means so that the adjusted axialthickness of the annular gap and therewith the adjusted throughput offluid can be easily observed, respectively set, by means of a pointerfixed to the screw for rotation therewith and a linear scale cooperatingwith the pointer.

The venturi arrangement of the present invention differs from theventuri arrangements known in the art in which the inflow as well as theoutflow of the fluid occurs in axial direction, in that, that in theventuri arrangement of the present invention only the inflow of thefluid occurs in axial direction, whereas the outflow downstream of thesmallest cross section of the annular gap occurs in a sheet like flow inradial outward direction. The axial smallest cross section of theannular gap is preferably arranged radially outwardly of the cylindricalinner surface of the inlet passage means. The inner end of the inletpassage means preferably gradually increases to blend into the smallestcross section of the annular gap.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings, inwhich:

FIG. 1 is a schematic axial cross section through the venturiarrangement of the present invention;

FIG. 2 is a partial cross section through a venturi arrangementaccording to the present invention and illustrating a differentarrangement for adjusting the position of the membrane;

FIG. 3 is a partial cross section similar to FIG. 1 and differingtherefrom mainly by the configuration of the annular gap; and

FIG. 4 is a partial cross section similar to FIG. 3 and showing afurther modification.

Referring now to the drawings and more specifically to FIG. 1 of thesame, it will be seen that the venturi arrangement according to thepresent invention comprises housing means including a first member 1having a central tubular portion 2 defining an inlet passage means forfeeding a fluid under pressure into the housing means. The first member1 includes further an annular plate-shaped portion 3 having preferablyan inner frustoconical surface 3' of a cone angle which is only slightlysmaller than 180 and the annular plate-shaped portion 3 is integrallyjoined at its inner periphery to the inner end of the tubular portion 2.At its outer periphery the annular plate-shaped portion 3 is integrallyjoined to an annular portion 7 defining an annular chamber 7, and

the annular portion 7 has an outer radial flange 9 spaced in axial andradial direction from the annular plateshaped portion 3. The innersurface of the central tubular portion 2 gradually blends into the innersurface of the plate-shaped portion 3 along a curve 4 which may have theshape of a quarter of a circle or a similar configuration so that fluidmay pass the inner end of the tubular portion 2 without turbulence.

The arrangement includes further, a second annular substantiallydisc-shaped member 11 having a central cylindrical flange 15 extendingin axial direction away from the central tubular portion 2 of the firstmember 1 and an outer flange 17 arranged opposite the flange 9 of thefirst member. A flexible membrane 10 overlays the inner surface of thesecond member 11 and the membrane 10- has an outer peripheral portiontightly clamped between the outer flanges 9 and 17 of the first andsecond member. A plurality of screws 16, only two of which are shown inFIG. 1', extend through appropriate bores in the flange 9 and in theouter periphery of the membrane 10 and are screwed with their ends intothreaded bores of the flange 17 to press the flanges 9 and 17 againsteach other so as to tightly clamp the outer peripheral portion of themembrane 10 between these flanges. Outlet passage means 8 in form of atube extending fluid-tightly connected to the transverse wall of theannular portion 7 communicates with the chamber means 7 formed by theannular portion 7 of the first member 1. The inner surface 3' of theannular plate-shaped portion 3 of the first member 1 forms with theinner surface of the membrane 10 facing the surface 3' an elongatedannular gap 6 having its narrowest cross section at 5 and the annulargap 6 in the embodiment illustrated in FIG. 1 gradually increases inthickness towards the annular chamber 7'.

To change the cross section of the annular gap 6 the arrangementaccording to the present invention preferably also comprises adjustingmeans and such adjusting means may include a piston 12 guided formovement in axial direction in the cylindrical flange 15 of the secondmember 11. The piston 12 engages with its preferably convexly curved endwall 13 a central portion of the flexible membrane 10 so that duringaxial movement of the piston 12 toward the inner end of the inletpassage means 2 the central portion of the membrane 6 may be inwardlydeflected to change thereby the narrowest cross section 5 of the annulargap 6. Inward movement of the piston 12 against the pressure of theliquid passing through the inlet passage 2 into the venturi arrangementmay be produced by a screw 14 abutting with one end thereof against thetransverse wall 13 of the piston 12. The screw 14 threadingly engages asupport member 16 connected in any manner, not shown in the drawing, tothe housing of the venturi arrangement and a small wheel 18 may befixedly connected to the outer end of the screw 14 for turning thelatter about its axis. The pitch of the screw thread of the screw 14 ispreferably chosen in such a way that the total desired axial adjustmentof the piston 12 may be obtained with a single revolution of the screw.A pointer 19 is preferably fixedly connected to the screw 14 and the endof the pointer 19 cooperates with a linear scale 20 provided on thesupport member 16 about the axis of the screw 14 so that the position ofthe screw and therewith the axial adjustment of the piston 12 can beeasily observed and set.

Instead of the adjusting screw 14 a spring abutting with one end againstthe transverse wall 13 of the piston 12 and with the other end thereofagainst a support member similar to the member 16 may also be providedto counteract the forces acting on the inner forces of the centralportion of the membrane. Such a spring may have any desiredpredetermined characteristic so that the spring pressure changes in anydesired manner with the change of the axial position of the piston 12and the spring pressure may also be adjusted by compressing the springto varying degree by changing the position of the support member againstwhich one end of the spring abuts.

A slightly modified arrangement is partly shown in FIG. 2 in which thecylindrical flange 15 of the member 11 is closed at its outer end and inwhich passage means 21 are provided which communicate at one end thereofwith the inlet passage means 2 and at the other end thereof with thespace between the piston 12 and the outer closed end of the cylindricalportion 15'. Such a passage 21 may be used in an arrangement in whichthe piston 12 is pushed inwardly by a rod 22 to which a variable forceis applied in axial direction and in which it is desired to change theaxial position of the piston 12 and therewith the axial cross section ofthe annular gap 6 in dependence on the variable force applied againstrod 22. The passage means 21 will assure that in this case the axialposition of the piston 12 is not influenced by variations of thepressure of the fluid passing through the inlet passage means 2, sincethe passage means 21 will equalize the pressure acting on opposite sidesof the central portion of the membrane 10, so that the axial position ofthe piston 12 and therefore the position of the central portion of themembrane will depend only on the force applied onto the rod 22.

While FIG. 1 illustrates an arrangement in which the axial thickness ofthe annular gap 6 gradually increases in radially outward direction,FIG. 3 shows anarrangement in which the inner surface 3" of theplate-shaped portion of the member 1 is parallel to the opposite surfaceof the second member 11 so that the axial thickness of the annular gap 6is constant throughout its length. FIG. 4 shows a further arrangement inwhich the inner surface 3 of the member 1" is inclined in the directionopposite to that shown in FIG. 1 so that the axial width of the annulargap 6" decreases gradually in radially outward direction. Instead ofconnecting the outer flanges 9 and 17 of the two members together byscrews 16, as shown in FIG. 1 it is also possible to Weld the twoflanges 9 and 17 and the outer peripheral portion of the membrane 10together as shown at 23 in FIGS. 3 and 4.

The inner surface of the membrane 10 and/ or the inner surface 3', 3" or3" may be roughened to provide for a pressure drop in the fluid passingbetween these surfaces.

The venturi arrangement above described may be used for control of fluid(amount of flow and mixture ratio of fuel and a combustion agent)independent of the pressure downstream of the venturi arrangement forrocket engines or other combustion engines, for feed control independentof the load acting on the feed mechanism in hydraulic devices,especially in machine tools. By use of metal membranes of appropriatematerial, it is possible to control and adjust the flow of aggressive orvery hot liquids, for instance also the flow of molten metals. This isespecially possible with the venturi arrangement according to thepresent invention in which no sealing means which would be attacked bysuch liquids are necessary and in which the members forming the housingof the venturi arrangement may be welded together. The venturiarrangement of the present invention can be used as a regulating valvewhich is independent from pressure variations downstream of the valve inall such cases Where a simple throttle valve is unsuitable or whereaxial cavitating venturi tubes, control pumps or other controlarrangements would be too expensive or not be suitable in view of thecharacteristics of the fluid medium to be controlled.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofventuri arrangements differing from the types described above.

While the invention has been illustrated and described as embodied in aventuri arrangement having an axial inlet passage and means to deflectthe flow of fluid in a sheet like annular stream in radial outwarddirection, it is not intended to be limited to the details shown, sincevarious modifications and structural changes may be made withoutdeparting in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a venturi arrangement for controlling flow of fluid, especiallyliquid, therethrough, in combination, housing means having an axialsubstantially cylindrical inlet passage means for feeding a fluid underpressure into said housing means, said inlet passage means having aninner end; and wall means defining an annular gap, said gap having aradial length which is a multiple of its maximum axial thickness, saidannular gap having its smallest peripheral cross section in the regionof said inner end of said passage means and said peripheral crosssection gradually increasing in radially outward direction to aperipheral cross section which is several times larger than saidsmallest peripheral cross section, said gap constituting means forcausing cavitation and partial evaporation of the fluid in said smallestperipheral cross section and subsequent recondensation of the fluidduring radial outward flow thereof for thereby producing a constantfluid flow through the arrangement substantially independent of pressurevariations downstream of said gap while the downstream fluid pressure isless than the inlet fluid pressure.

2. In a venturi arrangement as set forth in claim 1, and includingdeflector means extending substantially normal to the axis of said inletpassage means and arranged opposite and spaced from said inner endthereof for deflecting an axial stream of fluid passing through saidinlet passage means in radially outward direction, said annular gapextending in radial outward direction from the space between said innerend of said inlet passage means and said deflector means to guide thefluid in a sheet-like stream in radially outward direction.

3. In a venturi arrangement as set forth in claim 2, and including meansfor changing the axial thickness of said gap.

4. In a venturi arrangement as set forth in claim 2, wherein the axialthickness of said annular gap gradually increases from the radiallyinner to the readily outer end of said gap.

5. In a venturi arrangement as set forth in claim 4, wherein the shapeof the longitudinal cross section of said annular gap corresponds to thedesired speed of condensation of the fluid passing therethrough.

6. In a venturi arrangement as set forth in claim 2, wherein the axialthickness of said annular gap gradually changes from the radially innerto the radially outer end of said gap.

7. In a venturi arrangement as set forth in claim 6, wherein therelation of the cross section of said inlet passage means to that ofsaid narrowest portion of said annular gap is such that when gas at agiven pressure is fed through said inlet passage means into said housingmeans, said gas will reach sonic speed at said narrowest portion of saidgap to limit thereby the amount of gas flowing through the venturiarrangement substantially independent of pressure variations downstreamof said gap.

8. In a venturi arrangement as set forth in claim 2, and includingannular chamber means coaxially arranged about said inlet passage means,said annular gap extending from the space between said inner end of saidinlet passage means in radially outward direction to said annularchamber means, and outlet passage means communicating with said annularchamber means.

9. In a venturi arrangement as set forth in claim 8, wherein said wallmeans are arranged and constructed so that said annular gap has auniform axial thickness.

10. In a venturi arrangement as set forth in claim 8, wherein said Wallmeans are arranged and constructed so that said annular gap has an axialthickness gradually increasing toward said annular chamber means.

11. In a venturi arrangement as set forth in claim 8, wherein said wallmeans are arranged and constructed so that said annular gap has an axialthickness gradually decreasing toward said annular chamber means.

12. In a venturi arrangement as set forth in claim 8, and includingadjusting means operatively connected to said deflector means foradjusting the axial position thereof in order to vary the smallest crosssection of said gap to change thereby the flow of fluid through theventuri arrangement.

13. In a venturi arrangement as 'set forth in claim 8, wherein said wallmeans comprises a rigid annular wall integrally joined at the inner andouter periphery thereof to said inner end of said inlet passage meansand to said annular chamber means, respectively, and wherein saiddeflector means comprises a circular membrane having an inner surfacefacing an inner surface of said rigid annular wall and being spaced asmall distance therefrom and 'fluid-tightly joined at its outerperiphery to said annular chamber means, said annular gap being formedbetween said inner surface of said membrane and said inner surface ofsaid rigid annular Wall, and including means engaging that surface ofsaid membrane which faces away from said rigid wall at a substantiallycentral portion thereof in combination, housing means including a firstmember 1 having a central tubular portion defining an inlet passagemeans for feeding a fluid under pressure into said housing means, anannular plate-shaped portion extending transverse to the axis of saidtubular portion from the inner end of the latter and integrally'joinedat its inner periphery to said inner end, and an annular portiondefining an annular chamber arranged coaxially with said tubular portionand integrally joined to the outer periphery of said plate-shapedportion, said annular portion defining said annular chamber having anouter radial flange spaced in axial and radial direction from saidannular plateshaped portion; a second annular substantially disc-shapedmember having a central cylindrical flange extending in axial directionaway from said central tubular portion of said first member, and anouter radial flange opposite said outer flange of said first member,said second member having an inner surface axially spaced from an innersurface of said plate-shaped portion of said first member; a flexiblemembrane overlaying said inner surface of said second member and havingan outer peripheral portion tightly clamped between said outer flangesto define with said inner surface of said plate-shaped portion of saidfirst member an annular gap extending from the inner end of said centraltubular portion to said annular chamber so that a fluid fed through saidtubular portion into said housing means will be deflected in asheet-like stream passing through said annular gap into said annularchamher, said annular gap having a radial length which is a multiple ofits maximum axial thickness and said annular gap having its smallestperipheral cross section in the region of said inner end of said centraltubular portion and said peripheral cross section gradually increases inradially outward direction to a peripheral cross section which isseveral times larger than said smallest peripheral cross section, saidgap constituting means for causing cavitation and partial evaporation ofthe fluid in said smallest cross section and subsequent recondensationof the fluid as it passes toward said annular chamber for therebyproducing a constant fluid flow through the arrangement substantiallyindependent of pressure variations downstream of said gap while thedownstream fluid pressure is less than the inlet fluid pressure; meansfor connecting said outer flanges to each other with said outerperipheral portion of said flexible membrane tightly clamped betweensaid outer flanges; a piston member slidably guided in said centralcylindrical flange of said second member so as to be movable toward andaway from said inner end of said tubular portion, said piston memberengaging the outer surface of said membrane at a central portion thereofto change during axial adjustment of the position of said piston memberthe thickness of said annular gap so as to regulate the amount of fluidpassing therethrough; adjusting means operatively connected to saidpiston member for adjusting the axial position thereof; and outletpassage means communicating with said, annular chamber.

16. In a venturi arrangement as set forth in claim 15, wherein saidadjusting means comprise screw means operatively connected to saidpiston for adjusting the axial position thereof.

17. In a venturi arrangement as set forth in claim 15, and includingpassage means connecting said central tubular portion of said firstmember with said central cylindrical flange of said second member at theside of said piston member facing away from said membrane for applyingfluid at the same pressure as in said tubular portion to the side of thepiston member facing away from said membrane.

18. In a venturi arrangement as set forth in claim 15, wherein saidmeans for connecting said outer flanges comprise weld means for weldingsaid membrane in a fluidtight manner to said outer flanges.

References Cited UNITED STATES PATENTS 234,602 11/1880 Moore 251-282816,280 3/1906 Tuttle 138-44 1,986,600 1/1935 Pigott 251-124 X 2,918,93312/1959 Boitnott 251-124 X 3,003,743 10/ 196 1 Sattler 251-282 3,180,3604/1965 Pavlin 251-124 X 3,283,767 11/1966 Wright 137-815 2,875,9773/1959 Stone et al. 251-333 X FOREIGN PATENTS 1,155,578 12/1957 France.1,181,763 1/1959 France. 1,187,832 3/1959 France. 1,227,692 3/1960France.

842,565 6/ 1952 Germany.

795,192 5/1958 Great Britain.

895,517 5/ 1962 Great Britain.

M. CARY NELSON, Primary Examiner. R. C. MILLER, Assistant Examiner.

